Wire electric discharge machining (hereinafter referred to as “Wire EDM” or “WEDM”), also called Traveling Wire EDM, Wire Cutting or Wire Burning uses spark erosion to machine or remove electrically conductive material from a conductive workpiece with a continuous traveling electrode wire. The electrically conductive material is machined with a series of electrical discharges (sparks) that are produced between the electrode wire (the electrode) and the conductive workpiece. High frequency pulses of alternating or direct current are discharged from the electrode wire to the conductive workpiece with a very small spark gap through an insulated dielectric liquid. The heat of each electrical discharge (spark) erodes away a tiny bit of the electrically conductive material forming particles (also known as “chips”) that are vaporized and melted from the conductive workpiece in a cutting zone. These particles (chips) are flushed away from the cutting zone with a stream of the dielectric liquid through at least one flush nozzle in a wire EDM machine. The dielectric liquid also cools the electrode wire and prevents heat build-up in the conductive workpiece.
Higher cutting speeds and precision in wire EDM are ever increasing demands. The goal of higher cutting speed is dependent on the extent to which optimum conditions in the cutting zone may be established. Among other factors which govern these conditions, it has been recognized that adequate chip flushing is of particular importance. It is necessary that the cutting zone be flushed with the dielectric liquid in a sufficient volume and at a sufficiently high flow rate, yet uniformly along its entire length, i.e. across the thickness of the conductive workpiece, to allow the erosive action to continue with stability, the cutting chips and other erosive products to be carried away promptly from the cutting zone, and the electrode wire subject to erosive heating to be cooled with greater effectiveness. An orifice of the flush nozzle for delivering the dielectric liquid should be positioned as close as possible to the conductive workpiece to provide such adequate chip flushing. A conventional flush nozzle has a fixed length and therefore the orifice position of a conventional flush nozzle is not controllable once the conventional wire EDM machine has been configured. A conductive workpiece that has a flat top surface and a flat bottom surface permits tight nozzle contact for the best chip flushing. However, when the conductive workpiece top surface and/or bottom surface is not smooth or flat (i.e., the conductive workpiece has an irregular shape and/or surface that is not perpendicular to the electrode wire, i.e., is oblique), the ability of conventional flush nozzles to flush out the chips may be poor, resulting in decreased wire EDM efficiency.
Accordingly, it is desirable to provide variable length flush nozzles for wire EDM machines. It is also desirable that the length of the variable length flush nozzle automatically adjusts during wire EDM to maintain an orifice of the flush nozzle against the conductive workpiece regardless of the shape and/or surface thereof, resulting in improved chip flushing and an ability to wire EDM at the highest possible speed and precision. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the present invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.